There have been a lot of games where you were bound to your allies, but this is one of the few that joins you directly to your enemy. The AI difficulty levels were a nice touch. This game has a simple concept, but it was executed well--I could see it appearing on some game site like Nitrome back in the day!
I think the game could use some more depth, though--after a few games, you've experienced most of what the game has to offer. Maybe there are other minigame ideas you could implement with the features that are already present (like a co-op climbing/jumping minigame)?